Antennas are used to radiate and/or receive typically electromagnetic signals, preferably with antenna gain, directivity, and efficiency. Practical antenna design traditionally involves trade-offs between various parameters, including antenna gain, size, efficiency, and bandwidth.
Antenna design has historically been dominated by Euclidean geometry. In such designs, the closed area of the antenna is directly proportional to the antenna perimeter. For example, if one doubles the length of an Euclidean square (or “quad”) antenna, the enclosed area of the antenna quadruples. Classical antenna design has dealt with planes, circles, triangles, squares, ellipses, rectangles, hemispheres, paraboloids, and the like.
With respect to antennas, prior art design philosophy has been to pick a Euclidean geometric construction, e.g., a quad, and to explore its radiation characteristics, especially with emphasis on frequency resonance and power patterns. Unfortunately antenna design has concentrated on the ease of antenna construction, rather than on the underlying electromagnetics, which can cause a reduction in antenna performance.
This reduced antenna performance is evident in systems such as radio frequency identification (RFID) systems. RFID systems are used to track and monitor a variety of objects that range from commercial products and vehicles to even individual people. To track and monitor these objects an antenna and a radio frequency (RF) transceiver (together known as an RFID tag) are attached to the object. When an RF signal (usually transmitted from a handheld RF scanning device) is received by the RFID tag, the RF signal is used to transmit back another RF signal that contains information that identifies the object. However, an RFID tag's performance of can be affected by the environment in which it is placed. For example, performance of an antenna included in an RFID tag may be degraded by the object (e.g., a metallic shipping container, a car, etc.) to which it is attached. Due to this degradation, the RFID tag may need to be scanned multiple times and at a close range in order to activate the tag.